Currently, it is common to form various systems on semiconductor chips. General purpose processors, digital signal processors, Application Specific Integrated Circuits (ASICs), and the like are manufactured by forming a variety of transistors, memory elements, resistors, capacitors, inductors, etc., on a semiconductor substrate.
The processes that are used to form the circuit elements on a semiconductor substrate are sometimes less than ideal and cause some amount of process variation in the circuit elements. Variation, in general, is the difference between an actual quality of a circuit element and its nominal quality. For instance, capacitors formed in semiconductor chips tend to have process variation of up to approximately plus or minus 20%, depending on the fabrication process. Thus, the actual capacitance of a given capacitor on a chip, measured in Farads, may be significantly different from the intended or nominal value specified in the design. Inductors formed on semiconductor chips also generally experience some amount of variation, though less than that for capacitors, even on the same chip. Variation can also be a result of component temperature, age of components, and the like.
One application that uses capacitors is a tuner circuit. Specifically, such tuner circuits may include input filtering functions to condition input signals before they are passed to other tuner components. Most such filters are Inductive-Capacitive (LC) circuits. The frequency response of a given LC filter depends on the values of the capacitor(s) and inductor(s) in the circuit. Thus, capacitor variation can cause frequency response shifts in filters, causing non-ideal operation.
Tuners typically have Radio Frequency (RF) filters near the beginning of the signal path and Intermediate Frequency (IF) filters closer to the end of the signal path. When formed wholly or partly on a chip, such filters experience differences in their frequency responses due to the process variation. Currently, there is no technique offered that adjusts filters in the signal path based, at least in part, on LC variation during operation of a tuner.